How To Install Metal Roofing Over Existing Shingles. You must put in a completely new underlayment over the existing shingles before you carry out any installation. Both options have their benefits and drawbacks.
Do you have to remove shingles before installing a metal roof? Start with an underlayment over the existing shingles: Your metal trim will go along the roof's edges as well as the top ridge.
Installing steel roofing over existing roofing materials is fairly simple.
Do you have to remove shingles before installing a metal roof? This is the fastest way to install but it doesn’t provide the flattest surface for metal roofing installation. If you want to install steel over asphalt, your best choice for installing metal roofing is to use a steel shingle system like the one shown instead of the more common (and more expensive) standing seam steel. This is more expensive but will also be higher quality.